What is a "Matzeivah"?
Rashi and Ramban: It is a Mizbe'ach made of one stone, 1 even if it is built to sacrifice to Hashem. 2
Ramban: The "Matzeivah" mentioned in Bechukosai Vayikra, 26:1, however - "u'Fesel u'Matzeivah Lo Sakimu lachem" - refers to a Matzeivah that is made for the Pesel (the image) to stand on.
Why does the Torah juxtapose the Isur of erecting a Matzeivah to the perversion of judgment?
Targum Yonasan: To teach us that, just as one is forbidden to build a Matzeivah, so too, is one forbidden to appoint a community leader who is wicked - someone whom Hashem hates. 1
What is the difference between a Mizbe'ach, a Matzeivah and a Bamah?
Ramban: 'A Mizbe'ach' is a tall structure made of stones with four corners [on top], between which one offers Korbanos, and a base; 'A Matzeivah' comprises one large stone on which one offers incense or sacrifices, or for the priests to stand on. 1 'A Bamah' is like a hill 2 - it comprises a mound of earth on which a Mizbe'ach is built on which to sacrifice.
Ramban: In fact, every tall edifice is called a 'Bamah' - See Yeshayah, 14:14 & 32:13. See Ramban DH 've'Da'.
Bearing in mind that the Avos built Matzeivos, what caused Hashem to subsequently hate them?
Rashi and Ramban #1: Because the Nochrim adopted them as an integral part of their idolatry. 1
Ramban #2: Because the Cana'anim, who were addicted to idolatry, installed a Mizbe'ach in every house of idolatry, at the entrance of which they placed a large stone (Matzeivah), for the priests to stand on, 2 and outside there was a tree (an Asheirah) to attract the passersby. 3
Rashbam: Because they fall into the category of 'Bamos', which became forbidden once the Beis-Hamikdash was built. 4
Ramban: Because there was no house of idol-worship that did not have a Matzeivah on which to sacrifice and to pour oil. Hadar Zekenim (on Pasuk 21) ? any ritual of idolatry is forbidden even le'Shem Shamayim.
Ramban: 'In fact, the priests still do this today'.
Rashbam: As the Torah wrote in Re'ei, yyyyyyyyy12:8.
Seeing as after the time of the Avos, Hashem forbade Matzeivos, how could Moshe build twelve Matzeivos on Har Sinai (See Mishpatim, Sh'mos, 24:4)?
Oznayim la'Torah: Because Hashem only forbade Matzeivos after Matan Torah, 1 and Moshe built the Matzeivos before Matan Torah - as Rashi explains in Mishpatim. 2
Oznayim la'Torah (citing the Rashbam): Moshe did not build the Matzeivos in order to sacrifice Korbanos on them but merely as testimony that all the tribes entered into the B'ris with Hakadosh-Baruch-Hu. 3
Why did Hashem not forbid building a Mizbe'ach just like He forbade a Matzeivah, since the Nochrim also built Mizb'chos for Avodah-Zarah too?